Prior to the Internet, virtually all telephony calls were provided over the public switched telephone network (PSTN). The PSTN is a protected network where only authorized users have access. Further, the PSTN has mechanisms in place to ensure authorized users can take advantage of only those services for which they are authorized. As such, the PSTN provides significant control over who can make calls and how those calls are controlled.
As packet networks such as the Internet evolved, the ability to support packet-based telephony calls became a reality. The flexibility provided by packet networks has allowed disparate multimedia services to be associated for a much richer communication experience. The advent of gateways has allowed the packet networks and PSTN to cooperate with one another, such that a given telephony call can be supported over the Internet and the PSTN.
Unlike the PSTN, packet networks generally have an open architecture where virtually anyone can gain access and communicate as desired. Such openness has its benefits, but there are also numerous drawbacks. These drawbacks include the inability to control spammers and unscrupulous callers and vulnerability to security threats. As interworking between the PSTN, and the packet networks continues, these drawbacks are going to extend to the PSTN because the packet networks are going to provide unsecured access to the PSTN for various calls and multimedia sessions.
Accordingly, there is a need to provide more controlled and secure multimedia sessions, including telephony calls, over packet networks. There is a further need to ensure that the control and security limitations of existing packet-based sessions do not extend to the PSTN as interworking between the packet networks and PSTN evolves.